Method and system for redirection to arbitrary front-ends in a communication system

ABSTRACT

A system and method for providing network resources from an origin server to a client. A set of intermediary servers is topologically dispersed throughout a network. An enhanced communication channel is provided between the set of intermediary servers and the origin server. A redirector receives address resolution requests for the origin server, selects one of the intermediary servers in response to the request, and provides a network address of the selected intermediary servers to an entity generating the address resolution request.

RELATED APPLICATIONS

The present invention claims priority from U.S. Provisional PatentApplication No. 60/197,490 entitled CONDUCTOR GATEWAY filed on Apr. 17,2000.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates, in general, to network information accessand, more particularly, to software, systems and methods for serving webpages in a coordinated fashion from multiple cooperating web servers.

2. Relevant Background

Increasingly, business data processing systems, entertainment systems,and personal communications systems are implemented by computers acrossnetworks that are interconnected by Internetworks (e.g., the Internet).The Internet is rapidly emerging as the preferred system fordistributing and exchanging data. Data exchanges support applicationsincluding electronic commerce (e-commerce), broadcast and multicastmessaging, videoconferencing, gaming, and the like.

The Internet is a collection of disparate computers and networks coupledtogether by a web of interconnections using standardized communicationsprotocols. The Internet is characterized by its vast reach as a resultof its wide and increasing availability and easy access protocols.Unfortunately, the ubiquitous nature of the Internet results in variablebandwidth and quality of service between points. The latency andreliability of data transport is largely determined by the total amountof traffic on the Internet and so varies wildly seasonally andthroughout the day. Other factors that affect quality of service includeequipment outages and line degradation that force packets to bererouted, damaged and/or dropped. Also, routing software and hardwarelimitations within the Internet infrastructure may create bandwidthbottlenecks even when the mechanisms are operating withinspecifications.

Internet transport protocols do not discriminate between users. Datapackets are passed between routers and switches that make up theInternet fabric based on the hardware's instantaneous view of the bestpath between source and destination nodes specified in the packet.Because each packet may take a different path, the latency of a packetcannot be guaranteed and, in practice, varies significantly. Likewise,data packets are routed through the Internet without any prioritizationbased on content.

Prioritization has not been an issue with conventional networks such aslocal area networks (LANs) and wide area networks (WANs) because theaverage latency of such networks has been sufficiently low andsufficiently uniform to provide acceptable performance. However, thereis an increasing demand for network applications that cannot toleratehigh and variable latency. This situation is complicated when theapplication is to be run over the Internet where latency and variabilityin latency are many times greater than in LAN and WAN environments.

A particular need exists in environments that involve multiple usersaccessing a network resource such as a web server. Examples includebroadcast, multicast and videoconferencing as well as most electroniccommerce (e-commerce) applications. In these applications, it isimportant to maintain a reliable connection so that the server andclients remain synchronized and information is not lost.

In e-commerce applications, it is important to provide a satisfyingbuyer experience that leads to a purchase transaction. To provide thishigh level of service, a web site operator must ensure that data isdelivered to the customer in the most usable and efficient fashion.Also, the web site operator must ensure that critical data received fromthe customer is handled with priority.

Until now, however, the e-commerce site owner has had little or nocontrol over the transport mechanisms through the Internet that affectthe latency and quality of service. This is akin to a retailer beingforced to deal with a customer by shouting across the street, nevercertain how often what was said must be repeated, and knowing thatduring rush hour communication would be nearly impossible. While effortsare continually being made to increase the capacity and quality ofservice afforded by the Internet, it is contemplated that congestionwill always impact the ability to predictably and reliably offer aspecified level of service. Moreover, the change in the demand forbandwidth increases at a greater rate than does the change in bandwidthsupply, ensuring that congestion will continue to be an issue into theforeseeable future. A need exists for a system to exchange data over theInternet that provides a high quality of service even during periods ofcongestion.

Many e-commerce transactions are abandoned by the user because systemperformance degradations frustrate the purchaser before the transactionis consummated. While a transaction that is abandoned while a customeris merely browsing through a catalog may be tolerable, abandonment whenthe customer is just a few clicks away from a purchase is highlyundesirable. However, existing Internet transport mechanisms and systemsdo not allow the e-commerce site owner any ability to distinguishbetween the “just browsing” and the “about-to-buy” customers. In fact,the vagaries of the Internet may lead to the casual browser receiving ahigher quality of service while the about to buy customer becomesfrustrated and abandons the transaction.

Attempts have been made to cache web content at various cache serversdistributed across the Internet. Each cache server has a an explicitstatic IP address so as to enable the Internet domain name system to beused to locate cache servers. An HTTP request for a static element suchas an image, file or web page is handled by redirecting the clientmaking the request to a domain name corresponding to one of thedistributed caches. The client then generates requests directed at theselected cache server. These cache solutions do not affect the manner inwhich a connection is made between the client and the origin web serverand so are only partial solutions. Further, any content that is not orcannot be cached, such as dynamically generated content, must beobtained from the origin web server in a conventional way.

In a similar manner, web sites can be replicated or mirrored at variouslocations throughout the Internet. Mirror sites exist in a differentdomain than the origin site and so a user must be made aware of themirror's domain in order to use the mirror site. Because the user musttake explicit actions to access a mirror site, they are harder to use.Also, a user is often guessing at which mirror site will offer the bestperformance. A need exists for a system and method that enablesredirection to any of an arbitrary set of front end computers in acommunication system.

SUMMARY OF THE INVENTION

Briefly stated, the present invention involves a system and method forproviding network resources from an origin server to a client. A set ofintermediary servers is topologically dispersed throughout a network. Anenhanced communication channel is provided between the set ofintermediary servers and the origin server. A redirector receivesaddress resolution requests for the origin server, selects one of theintermediary servers in response to the request, and provides a networkaddress of the selected intermediary servers to an entity generating theaddress resolution request.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a general distributed computing environment in whichthe present invention is implemented;

FIG. 2 shows in block-diagram form significant components of a system inaccordance with the present invention;

FIG. 3 shows a domain name system used in an implementation of thepresent invention;

FIG. 4 shows front-end components of FIG. 2 in greater detail;

FIG. 5 shows back-end components of FIG. 2 in greater detail;

FIG. 6 shows a functional block diagram of a redirection mechanism inaccordance with the present invention;

FIG. 7 illustrates a conceptual diagram showing entity relationshipsmaintained by the system in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is illustrated and described in terms of adistributed computing environment such as an enterprise computing systemusing public communication channels such as the Internet. However, animportant feature of the present invention is that it is readily scaledupwardly and downwardly to meet the needs of a particular application.Accordingly, unless specified to the contrary, the present invention isapplicable to significantly larger, more complex network environments,including wireless network environments, as well as small networkenvironments such as conventional LAN systems.

The present invention involves a redirector system that functions toredirect web browser software that is “visiting” a particular web siteto an appropriate front-end computer or intermediate computer for thatsite. The redirector mechanism is intended to be highly fault-tolerant,capable of handling significant numbers of redirection requests withnear-zero downtime. The redirector represents a modified form of DNS(Domain Name Server). When a request is received to provide the IPaddress for a given domain name, redirector 309 instead provides the IPaddress of the best available front-end server 201. In contrast,conventional redirection sends a redirected domain name to the webbrowser, which in turn determines the redirected IP address using theconventional DNS. In accordance with the present invention, the browserhas no knowledge that it has been redirected, and is a passiveparticipant in the redirection process.

One feature of the present invention is that the front-end servers arein separate IP address domains from the originating web server. Aredirection mechanism is enabled to select from an available pool offront-end servers and direct client request packets from the originatingweb server to a selected front-end server. Preferably, the front-endserver establishes and maintains an enhanced communication channel withthe originating web server. By enhanced it is meant that the enhancedchannel offers improved quality of service, lower latency,prioritization services, higher security transport, or other featuresand services that improve upon the basic transport mechanisms (such asTCP) defined for Internet data transport.

For purposes of this document, a web server is a computer running serversoftware coupled to the World Wide Web (i.e., “the web”) that deliversor serves web pages. The web server has a unique IP address and acceptsconnections in order to service requests by sending back responses. Aweb server differs from a proxy server or a gateway server in that a webserver has resident a set of resources (i.e., software programs, datastorage capacity, and/or hardware) that enable it to execute programs toprovide an extensible range of functionality such as generating webpages, accessing remote network resources, analyzing contents ofpackets, reformatting request/response traffic and the like using theresident resources. In contrast, a proxy simply forwardsrequest/response traffic on behalf of a client to resources that resideelsewhere, or obtains resources from a local cache if implemented. A webserver in accordance with the present invention may reference externalresources. Commercially available web server software includes MicrosoftInternet Information Server (IIS), Netscape Netsite, Apache, amongothers. Alternatively, a web site may be implemented with custom orsemi-custom software that supports HTTP traffic.

FIG. 1 shows an exemplary computing environment 100 in which the presentinvention may be implemented. Environment 100 includes a plurality oflocal networks such as Ethernet network 102, FDDI network 103 and Tokenring network 104. Essentially, a number of computing devices and groupsof devices are interconnected through a network 101. For example, localnetworks 102, 103 and 104 are each coupled to network 101 throughrouters 109. LANs 102, 103 and 104 may be implemented using anyavailable topology and may implement one or more server technologiesincluding, for example a UNIX, Novell, or Windows NT networks, includingclient/server and peer-to-peer type networking. Each network willinclude distributed storage implemented in each device and typicallyincludes some mass storage device coupled to or managed by a servercomputer. Network 101 comprises, for example, a public network, such asthe Internet, or another network mechanism, such as a fibre channelfabric or conventional WAN technologies.

Local networks 102, 103 and 104 include one or more network appliances107. One or more network appliances 107 may be configured as anapplication and/or file server. Each local network 102, 103 and 104 mayinclude a number of shared devices (not shown) such as printers, fileservers, mass storage and the like. Similarly, devices 111 may be sharedthrough network 101 to provide application and file services, directoryservices, printing, storage, and the like. Routers 109 which existthroughout network 101 as well as at the edge of network 101 as shown inFIG. 1, provide a physical connection between the various devicesthrough network 101. Routers 109 may implement desired access andsecurity protocols to manage access through network 101.

Network appliances 107 may also couple to network 101 through publicswitched telephone network (PSTN) 108 using copper or wirelessconnection technology. In a typical environment, an Internet serviceprovider 106 supports a connection to network 101 as well as PSTN 108connections to network appliances 107.

Network appliances 107 may be implemented as any kind of networkappliance having sufficient computational function to execute softwareneeded to establish and use a connection to network 101. Networkappliances 107 may comprise workstation and personal computer hardwareexecuting commercial operating systems such as Unix variants, MicrsosoftWindows, Macintosh OS, and the like. At the same time, some appliances107 comprise portable or handheld devices such as personal digitalassistants and cell phones executing operating system software such asPalmOS, WindowsCE, EPOC OS and the like. Moreover, the present inventionis readily extended to network devices such as office equipment,vehicles, and personal communicators that occasionally connect throughnetwork 101.

Each of the devices shown in FIG. 1 may include memory, mass storage,and a degree of data processing capability sufficient to manage theirconnection to network 101. The computer program devices in accordancewith the present invention are implemented in the memory of the variousdevices shown in FIG. 1 and enabled by the data processing capability ofthe devices shown in FIG. 1. In addition to local memory and storageassociated with each device, it is often desirable to provide one ormore locations of shared storage such as disk farm (not shown) thatprovides mass storage capacity beyond what an individual device canefficiently use and manage. Selected components of the present inventionmay be stored in or implemented in shared mass storage.

The present invention operates in a manner akin to a private network 200implemented within the Internet infrastructure. Private network 200expedites and prioritizes communications between a client 205 and a website 210. In the specific examples herein client 205 comprises anetwork-enabled graphical user interface such as a World Wide Webbrowser. However, the present invention is readily extended to clientsoftware other than conventional World Wide Web browser software. Anyclient application that can access a standard or proprietary user levelprotocol for network access is a suitable equivalent. Examples includeclient applications for file transfer protocol (FTP) services, voiceover Internet protocol (VOIP) services, network news protocol (NNTP)services, multi-purpose internet mail extensions (MIME) services, postoffice protocol (POP) services, simple mail transfer protocol (SMTP)services, as well as Telnet services. In addition to network protocols,the client application may access a network application such as adatabase management system (DBMS) in which case the client applicationgenerates query language (e.g., structured query language or “SQL”)messages. In wireless appliances, a client application may communicatevia a wireless application protocol (WAP) or the like.

For convenience, the term “web site” is used interchangeably with “webserver” in the description herein, although it should be understood thata web site comprises a collection of content, programs and processesimplemented on one or more web servers. A web site is owned by thecontent provider such as an e-commerce vendor, whereas a web serverrefers to set of programs running on one or more machines coupled to anInternet node. The web site 210 may be hosted on the site owner's ownweb server, or hosted on a web server owned by a third party. A webhosting center is an entity that implements one or more web sites on oneor more web servers using shared hardware and software resources acrossthe multiple web sites. In a typical web infrastructure, there are manyweb browsers, each of which has a TCP connection to the web server inwhich a particular web site is implemented. The present invention addstwo components to the infrastructure: a front-end server 201 andback-end 203. Front-end 201 and back-end 203 are coupled by a manageddata communication link 202 that forms, in essence, a private network.

Front-end server 201 serves as an access point for client-sidecommunications. Front-end server 201 implements a gateway that functionsas a proxy for the web server(s) implementing web site 210 (i.e., fromthe perspective of client 205, front-end server 201 appears to be theweb site 210). Front-end server 201 comprises, for example, a computerthat sits “close” to clients 205. By “close”, it is meant that theaverage latency associated with a connection between a client 205 and afront-end server 201 is less than the average latency associated with aconnection between a client 205 and a web site 210. Desirably, front-endservers have as fast a connection as possible to the clients 205. Forexample, the fastest available connection may be implemented in point ofpresence (POP) of an Internet service provider (ISP) 106 used by aparticular client 205. However, the placement of the front-end servers201 can limit the number of browsers that can use them. Because of this,in some applications it is more practical to place one front-end servercomputer in such a way that several POPs can connect to it. Greaterdistance between front-end server 201 and clients 205 may be desirablein some applications as this distance will allow for selection amongst agreater number front-end servers 201 and thereby provide significantlydifferent routes to a particular back-end server 203. This may offerbenefits when particular routes and/or front-end servers becomecongested or otherwise unavailable.

Transport mechanism 202 is implemented by cooperative actions of thefront-end server 201 and back-end server 203. Back-end server 203processes and directs data communication to and from web site 210.Transport mechanism 202 communicates data packets using a proprietaryprotocol over the public Internet infrastructure in the particularexample. Hence, the present invention does not require heavyinfrastructure investments and automatically benefits from improvementsimplemented in the general purpose network 101. Unlike the generalpurpose Internet, front-end server 201 and back-end server 203 areprogrammably assigned to serve accesses to a particular web site 210 atany given time.

It is contemplated that any number of front-end server and back-endserver mechanisms may be implemented cooperatively to support thedesired level of service required by the web site owner. The presentinvention implements a many-to-many mapping of front-end servers toback-end servers. Because the front-end server to backend servermappings can by dynamically changed, a fixed hardware infrastructure canbe logically reconfigured to map more or fewer front-end servers to moreor fewer backends and web sites or servers as needed.

Front-end server 201 together with back-end server 203 function toreduce traffic across a transport morphing protocol™ (TMP™) link 202 andto improve response time for selected browsers. Transport morphingprotocol and TMP are trademarks or registered trademarks of CircadenceCorporation in the United States and other countries. Traffic across theTMP link 202 is reduced by compressing data and serving browser requestsfrom cache for fast retrieval. Also, the blending of request datagramsresults in fewer request:acknowledge pairs across the TMP link 202 ascompared to the number required to send the packets individually betweenfront-end server 201 and back-end server 203. This action reduces theoverhead associated with transporting a given amount of data, althoughconventional request:acknowledge traffic is still performed on the linkscoupling the front-end server 201 to client 205 and back-end server 203to a web server. Moreover, resend traffic is significantly reducedfurther reducing the traffic. Response time is further improved forselect privileged users and for specially marked resources bydetermining the priority for each HTTP transmission.

In one embodiment, front-end server 201 and back-end server 203 areclosely coupled to the Internet backbone. This means they have highbandwidth connections, can expect fewer hops, and have more predictablepacket transit time than could be expected from a general-purposeconnection. Although it is preferable to have low latency connectionsbetween front-end servers 201 and back-end servers 203, a particularstrength of the present invention is its ability to deal with latency byenabling efficient transport and traffic prioritization. Hence, in otherembodiments front-end server 201 and/or back-end server 203 may belocated farther from the Internet backbone and closer to clients 205and/or web servers 210. Such an implementation reduces the number ofhops required to reach a front-end server 201 while increasing thenumber of hops within the TMP link 202 thereby yielding control overmore of the transport path to the management mechanisms of the presentinvention.

Clients 205 no longer conduct all data transactions directly with theweb server 210. Instead, clients 205 conduct some and preferably amajority of transactions with front-end servers 201, which simulate thefunctions of web server 210. Client data is then sent, using TMP link202, to the back-end server 203 and then to the web server 210. Runningmultiple clients 205 over one large connection provides severaladvantages:

-   -   Since all client data is mixed, each client can be assigned a        priority. Higher priority clients, or clients requesting higher        priority data, can be given preferential access to network        resources so they receive access to the channel sooner while        ensuring low-priority clients receive sufficient service to meet        their needs.    -   The large connection between a front-end server 201 and back-end        server 203 can be permanently maintained, shortening the many        TCP/IP connection sequences normally required for many clients        connecting and disconnecting.        Using a proprietary protocol allows the use of more effective        techniques to improve data throughput and makes better use of        existing bandwidth during periods when the network is congested.

A particular advantage of the architecture shown in FIG. 2 is that it isreadily scaled. Any number of client machines 205 may be supported. In asimilar manner, a web site owner may choose to implement a site usingmultiple web servers 210 that are co-located or distributed throughoutnetwork 101. To avoid congestion, additional front-end servers 201 maybe implemented or assigned to particular web sites. Each front-endserver 201 is dynamically re-configurable by updating address parametersto serve particular web sites. Client traffic is dynamically directed toavailable front-end servers 201 to provide load balancing. Hence, whenquality of service drops because of a large number of client accesses,an additional front-end server 201 can be assigned to the web site andsubsequent client requests directed to the newly assigned front-endserver 201 to distribute traffic across a broader base.

In the particular examples, this is implemented by a front-end managercomponent 207 that communicates with multiple front-end servers 201 toprovide administrative and configuration information to front-endservers 201. Each front-end server 201 includes data structures forstoring the configuration information, including information identifyingthe IP addresses of web servers 210 to which they are currentlyassigned. Other administrative and configuration information stored infront-end server 201 may include information for prioritizing data fromand to particular clients, quality of service information, and the like.

Similarly, additional back-end servers 203 can be assigned to a web siteto handle increased traffic. Backend manager component 209 couples toone or more back-end servers 203 to provide centralized administrationand configuration service. Back-end servers 203 include data structuresto hold current configuration state, quality of service information andthe like. In the particular examples front-end manager 207 and back-endmanager 209 serve multiple web sites 210 and so are able to manipulatethe number of front-end servers and back-end servers assigned to eachweb site 210 by updating this configuration information. When thecongestion for the site subsides, the front-end server 201 and back-endserver 203 can be reassigned to other, busier web sites. These andsimilar modifications are equivalent to the specific examplesillustrated herein.

In the case of web-based environments, front-end server 201 isimplemented using custom or off-the-shelf web server software. Front-endserver 201 is readily extended to support other, non-web-basedprotocols, however, and may support multiple protocols for varieties ofclient traffic. Front-end server 201 processes the data traffic itreceives, regardless of the protocol of that traffic, to a form suitablefor transport by TMP 202 to a back-end server 203. Hence, most of thefunctionality implemented by front-end server 201 is independent of theprotocol or format of the data received from a client 205. Hence,although the discussion of the exemplary embodiments herein relatesprimarily to front-end server 201 implemented as a web server, it shouldbe noted that, unless specified to the contrary, web-based trafficmanagement and protocols are merely examples and not a limitation of thepresent invention.

As shown in FIG. 2, in accordance with the present invention a web siteis implemented using an originating web server 210 operatingcooperatively with the web server of front-end server 201. Moregenerally, any network service (e.g., FTP, VoIP, NNTP, MIME, SMTP,Telnet, DBMS) can be implemented using a combination of an originatingserver working cooperatively with a front-end server 201 configured toprovide a suitable interface (e.g., FTP VoIP, NNTP, MIME, SMTP, Telnet,DBMS, WAP) for the desired service. In contrast to a simple front-endcache or proxy software, implementing a server in front-end server 201enables portions of the web site (or other network service) to actuallybe implemented in and served from both locations. The actual web pagesor service being delivered comprises a composite of the portionsgenerated at each server. Significantly, however, the web server infront-end server 201 is close to the browser in a client 205 whereas theoriginating web server is close to all resources available at the webhosting center at which web site 210 is implemented. In essence the website 210 is implemented by a tiered set of web servers comprising afront-end server 201 standing in front of an originating web server.

This difference enables the web site or other network service to beimplemented so as to take advantage of the unique topological positioneach entity has with respect to the client 205. By way of a particularexample, assume an environment in which the front-end server 201 islocated at the location of an ISP used by a particular set of clients205. In such an environment, clients 205 can access the front-end server205 without actually traversing the network 101.

In order for a client 205 to obtain service from a front-end server 201,it must first be directed to a front-end server 201 that can provide thedesired service. Preferably, client 205 does not need to be aware of thelocation of front-end server 201, and initiates all transactions as ifit were contacting the originating server 210. FIG. 3 illustrates adomain name server (DNS) redirection mechanism that illustrates how aclient 205 is connected to a front-end server 201. The DNS systems isdefined in a variety of Internet Engineering Task Force (IETF) documentssuch as RFC0883, RFC 1034 and RFC 1035 which are incorporated byreference herein. In a typical environment, a client 205 executes abrowser 301, TCP/IP stack 303, and a resolver 305. For reasons ofperformance and packaging, browser 301, TCP/IP stack 303 and resolver305 are often grouped together as routines within a single softwareproduct.

Browser 301 functions as a graphical user interface to implement userinput/output (I/O) through monitor 311 and associated keyboard, mouse,or other user input device (not shown). Browser 301 is usually used asan interface for web-based applications, but may also be used as aninterface for other applications such as email and network news, as wellas special-purpose applications such as database access, telephony, andthe like. Alternatively, a special-purpose user interface may besubstituted for the more general purpose browser 301 to handle aparticular application.

TCP/IP stack 303 communicates with browser 301 to convert data betweenformats suitable for browser 301 and IP format suitable for Internettraffic. TCP/IP stack also implements a TCP protocol that managestransmission of packets between client 205 and an Internet serviceprovider (ISP) or equivalent access point. IP protocol requires thateach data packet include, among other things, an IP address identifyinga destination node. In current implementations the IP address comprisesa 32-bit value that identifies a particular Internet node. Non-IPnetworks have similar node addressing mechanisms. To provide a moreuser-friendly addressing system, the Internet implements a system ofdomain name servers that map alpha-numeric domain names to specific IPaddresses. This system enables a name space that is more consistentreference between nodes on the Internet and avoids the need for users toknow network identifiers, addresses, routes and similar information inorder to make a connection.

The domain name service is implemented as a distributed database managedby domain name servers (DNSs) 307 such as DNS_A, DNS_B and DNS_C shownin FIG. 3. Each DNS relies on <domain name:IP> address mapping datastored in master files scattered through the hosts that use the domainsystem. These master files are updated by local system administrators.Master files typically comprise text files that are read by a local nameserver, and hence become available through the name servers 307 to usersof the domain system.

The user programs (e.g., clients 205) access name servers throughstandard programs such as resolver 305. Resolver 305 includes an addressof a DNS 307 that serves as a primary name server. When presented with areference to a domain name (e.g., http://www.circadence.com), resolver305 sends a request to the primary DNS (e.g., DNS_A in FIG. 3). Theprimary DNS 307 returns either the IP address mapped to that domainname, a reference to another DNS 307 which has the mapping information(e.g., DNS_B in FIG. 3), or a partial IP address together with areference to another DNS that has more IP address information. Anynumber of DNS-to-DNS references may be required to completely determinethe IP address mapping.

In this manner, the resolver 305 becomes aware of the IP address mappingwhich is supplied to TCP/IP component 303. Client 205 may cache the IPaddress mapping for future use. TCP/IP component 303 uses the mapping tosupply the correct IP address in packets directed to a particular domainname so that reference to the DNS system need only occur once.

In accordance with the present invention, at least one DNS server 307 isowned and controlled by system components of the present invention. Whena user accesses a network resource (e.g., a web site), browser 301contacts the public DNS system to resolve the requested domain name intoits related IP address in a conventional manner. In a first embodiment,the public DNS performs a conventional DNS resolution directing thebrowser to an originating server 210 and server 210 performs aredirection of the browser to the system owned DNS server (i.e., DNC_Cin FIG. 3). In a second embodiment, domain:address mappings within theDNS system are modified such that resolution of the of the originatingserver's domain automatically return the address of the system-owned DNSserver (DNS_C). Once a browser is redirected to the system-owned DNSserver, it begins a process of further redirecting the browser 301 tothe best available front-end server 201.

Unlike a conventional DNS server, however, the system-owned DNS_C inFIG. 3 receives domain:address mapping information from a redirectorcomponent 309. Redirector 309 is in communication with front-end manager207 and back-end manager 209 to obtain information on current front-endand back-end assignments to a particular server 210. A conventional DNSis intended to be updated infrequently by reference to its associatedmaster file. In contrast, the master file associated with DNS_C isdynamically updated by redirector 309 to reflect current assignment offront-end server 201 and back-end server 203. In operation, a referenceto web server 210 (e.g., http://www.circadence.com) may result in an IPaddress returned from DNS_C that points to any selected front-end server201 that is currently assigned to web site 210. Likewise, web site 210can identify a currently assigned back-end server 203 by direct orindirect reference to DNS_C.

Front-end server 201 typically receives information directly fromfront-end server manager 207 about the address of currently assignedback-end servers 203. Similarly, back-end server 203 is aware of theaddress of a front-end server 201 associated with each data packet.Hence, reference to the domain system is not required to map a front-endserver 201 to its appropriate back-end server 203.

FIG. 6 shows an exemplary implementation of redirector 309 in accordancewith the present invention. Redirector 309 is implemented as amulti-level set of redirector servers that cooperate to determine an IPaddress for a particular front-end server 201 out of a pool of otherwisearbitrary or generic front-end servers 201. When a global redirectorserver 309 receives a request for domain name resolution, it estimatesthe global region from which the request came using knowledge about IPaddress space allocated to particular global region. Third-partyservices (such as NetGeo) are available that provide such IP address“maps”. The user will be redirected to a selected regional redirectorserver 603 which serves that region. The term “region” refers to portionof the Internet, which could be associated with a part of a country(e.g. southern United States), a country (e.g. Japan), or an entiregeographic area (e.g. Western Europe). Such a determination is based onthe Internet topology, not the global population.

Once the user has been redirected to regional redirector server 603 intheir home region, regional redirector server 603 takes over the processof finding the single best gateway front-end server 201 for the user.Regional redirector 603 identifies a network where the user is located.The “network” in which the user is located refers to a set of one ormore front-end servers 201 connected to the same network redirector 604.On any given “network”, for any given back-end server 203 (shown in FIG.2), there must be at least one front-end server 201 connected to thatback-end server 203. It is possible that regional redirector 603 mightmiscalculate the user's location and redirects that user to the wrongnetwork redirector 604. In that situation, the selected networkredirector 604 will not reject the user, but will do its best tocalculate and return the address of its best available front-end server201.

In the preferred implementations, each front-end server 201 supports acommunication channel with each back-end server 203. Hence, there exista large number of alternative channels that may be selected to providesuitable service for a given connection. The best available front-endserver 201 is determined based on estimates and actual measurements ofquality of service that can be provided by the various alternativechannels.

In accordance with the present invention, network redirector 604determines a quality of service index or factor for each of a pluralityof the available alternative channels. This quality of service indextakes into account a variety of component factors such as latency, lostpackets, server load (e.g., CPU usage) within the various front-endservers 201 and back-end servers 203, and the like. This index alsoattempts to account for components that affect the connection between aclient 205 and each front-end server 201, although these factors may notbe determinable with precision. Based upon the client's IP address,redirector 604 can estimate the geographic or topological distancebetween each front-end server 201 and estimate the quality of service ofthe alternate links. For example, it might often be true that afront-end server 201 that is close to client 205 will provide superiorservice.

The various component factors are combined arithmetically or logicallyto generate an index. The combination might be a simple addition ormultiplication operation, or may involve weighting each of the componentfactors. Based upon the determined index, a front-end server 201 can beselected from the arbitrary set of available front-end servers 201. Thenetwork address (e.g., IP address) for the selected front-end server 201is communicated to client 205 in response to the domain resolutionrequest issued by client 205. Henceforth, client 205 maintains theassociation between the requested domain (www.abc.com) and the returnedIP address of the selected front-end server 201. From the client'sperspective, the server found at the returned IP address is within theaddress domain of the requested web site 210.

If a regional redirector 603 were to be off-line, the user's requestwould fail. To avoid this situation, it is desirable that each regionalredirector 603 will be served by at least two computers, to be known asprimary and secondary. For regions with significant traffic, it may beadvisable to deploy not only primary and secondary computers, buttertiary computers as well.

Front-end servers 201 report their status on a regular basis to theirnetwork redirector 604. It is possible that a specific front-end server201 might go down without the network redirector 604 becomingimmediately aware. In that situation, a user's request would not fail.Network redirectors 604 will return not one, but two or three IPaddresses of different front-end server computers 201. As a result, ifone front-end server is down, the user will be automatically connectedto another front-end server 201. It is expected that redirectormechanism 309 will usually realize the unavailability of a front-endserver 201 in less than one minute, although the time in a particularimplementation may be selected to meet the needs of that implementation.

In cases where regional redirector 603 is unable to identify the networkthat the user belongs to, it will try to find an alternate networkclosest to that user, and will redirect that users to the networkredirector 604 that serves this alternate network. The selected networkredirector 604 completes the process of selecting the most suitablefront-end server 201 for a user. The redirector makes a decision byconsidering several factors that may include:

-   -   processor load of available front-end servers 201;    -   cost of connection in terms of resources and time to configure        those resources between the various available front-end servers        201 and the desired back-end server 203;    -   estimated topological distance and latency between the client        and the available front-end servers 201;    -   estimated topological distance and latency between the available        front-end servers 201 and the web site;    -   estimated cost of connection;    -   ability of the various available front-ends 201 to serve the        specific web site 210 (i.e. the content and functionality of web        site 210 currently housed on front-ends 201.

Finding the absolute best available front-end server 201 may, in somecases, take too long. If this is the case for a given search, the searchprocess could be curtailed in several ways:

-   -   If a satisfactory front-end server 201 is found (with a        predetermined acceptable suitability value);    -   If a timer runs out, in which case the “best yet” front-end        server 201 would be used.

Having selected a front-end server 201, the user is connected to theselected front-end server and the job of redirector 309 is complete. Ina particular example, front-end servers 201 communicate only with theircorresponding network redirector servers 604. As a result, the user willalmost always be sent to a front-end server 201 that is topologicallyclose, for example in their home region, even if not the first “best”choice. Communications between the front-end server computers 201 andthe redirector 309 are preferably secure and fault-tolerant.

A special case exists for secure communications. When a client sends apacket using secure HTTP, for example, the payload is encrypted in amanner that only the origin server 210 can decrypt. While the originserver could share its decryption keys with front-ends 201, this mayreduce the integrity of the keys to an unacceptable degree owing to thewider distribution of the keys. Hence, a front-end 201 will be unable toparse and process secure packets in the same manner as it is able towork with conventional packets.

In many cases, secure communications use a specially designated port onthe sending and receiving machines. For example, conventional HTTPtraffic uses port 80 whereas secure HTTP (HTTPS) uses port 443. Whileother ports can be designated, standard-compliant TCP/IP processes willlisten for secure communication on port 443 by default. In these cases,when the client sends a communication on the secure port the back-end203 should deliver the packet on the secure port.

In accordance with an embodiment of the present invention, redirector309 specifies a secure port (e.g., port 443) of the selected front-end201 in the IP address returned to a client 205. Further, front-end 201implements processes that listen to the secure port and handle packetsreceived on the secure port specially. These packets may be blended withnon-secure packets over TMP link 202. However, packets received on asecure port, or any other non-standard port, are marked or tagged withthe port number on which they should be delivered. This enables aback-end 203 to address the server 210 on the same port that client 205intended to send the packet.

Each front-end server 201 regularly reports its status to its networkredirector server 604. Once a new front-end server 201 comes online, theredirector 309 would immediately become aware of this new front-endserver 201, as well as all back-end servers 203 connected to thatfront-end server. Should a front-end server 201 become unavailable, theredirector 309 will find out quickly, preferably in less than oneminute. This small potential downtime can be reduced even further bymeans of an optional, third layer of DNS servers.

It is important to prevent the network redirector servers from beingmisled. Communications between redirector 309 and the front-end servers201 is preferably secure. Secure connections can be ensured in multipleways:

-   -   encrypting communications between these systems;    -   using a fixed list of front-end servers 201 each having a known        address and ensuring that redirector 309 or network redirector        604 confirms that all messages it receives are from trusted        sources; and    -   sending communications between the systems over an out-of-band        connection.

The redirection system in accordance with the present invention isusefully understood in contrast with a conventional DNS system. Aconventional DNS is intended to be updated infrequently by reference toits associated master file. In contrast, the master file associated withDNS_C is dynamically updated by redirector 309 to reflect currentassignment of front-end server 201 and back-end server 203. Inoperation, a reference to web server 210 (e.g., http://www.abc.com) mayresult in an IP address returned from redirector 309 that points to aselected front-end server 201.

Front-end server 201 typically receives information directly fromfront-end manager 207 about the address of currently assigned back-endservers 203. Similarly, back-end server 203 is aware of the address of afront-end server 201 associated with each data packet. Managementutilities will be required to administer the redirector system 309. Theglobal, regional and network DNS servers may require separate utilities.The following is an exemplary list of tasks that the managementutilities for redirector system 309 may perform:

-   -   Update list of regional redirectors 603 known to global        redirector 601;    -   Update list of network redirectors 604 known to regional        redirector 603;    -   Update list of front-end servers 201 known by network        redirectors 604;    -   Modify subset of criteria used to determine and select best        front-end server 201 available; and    -   Report current and historical statistics.

Returning now to FIG. 4, principle functional components of an exemplaryfront-end server 201 are illustrated in greater detail. Primaryfunctions of the front-end server 201 include translating transmissioncontrol protocol (TCP) packets from client 205 into TMP packets used inthe system in accordance with the present invention. It is contemplatedthat the various functions described in reference to the specificexamples may be implemented using a variety of data structures andprograms operating at any location in a distributed network. Forexample, a front-end server 201 may be operated on a network appliance107 or server within a particular network 102, 103, or 104 shown inFIG. 1. The present invention is readily adapted to any applicationwhere multiple TCP clients are coupling to a centralized TCP resource.Moreover, other transport control protocols may be used, includingproprietary transport protocols, so long as the transport protocolssupply the functionality of the TCP protocol.

TCP component 401 includes devices for implementing physical connectionlayer and Internet protocol (IP) layer functionality. Current IPstandards are described in IETF documents RFC0791, RFC0950, RFC0919,RFC0922, RFC792, RFC1112 that are incorporated by reference herein. Forease of description and understanding, these mechanisms are notdescribed in great detail herein.

TCP component 401 communicates TCP packets with one or more clients 205.Received packets are coupled to parser 402 where the Internet protocol(or equivalent) information is extracted. TCP is described in IETFRFC0793 which is incorporated herein by reference. Each TCP packetincludes header information that indicates addressing and controlvariables, and a payload portion that holds the user-level data beingtransported by the TCP packet. The user-level data in the payloadportion typically comprises a user-level network protocol datagram.

Parser 402 analyzes the payload portion of the TCP packet. In theexamples herein, HTTP is employed as the user-level protocol because ofits widespread use and the advantage that currently available browsersoftware is able to readily use the HTTP protocol. In this case, parser402 comprises an HTTP parser. More generally, parser 402 can beimplemented as any parser-type logic implemented in hardware or softwarefor interpreting the contents of the payload portion. Parser 402 mayimplement file transfer protocol (FTP), mail protocols such as simplemail transport protocol (SMTP), structured query language (SQL) and thelike. Any user-level protocol, including proprietary protocols, may beimplemented within the present invention using appropriate modificationof parser 402.

To improve performance, front-end server 201 optionally includes acaching mechanism 403. Cache 403 may be implemented as a passive cachethat stores frequently and/or recently accessed web pages or as anactive cache that stores network resources that are anticipated to beaccessed. In non-web applications, cache 403 may be used to store anyform of data representing database contents, files, program code, andother information. Upon receipt of a TCP packet, HTTP parser 402determines if the packet is making a request for data within cache 403.When the request can be satisfied from cache 403, the data is supplieddirectly without reference to web server 210 (i.e., a cache hit). Cache403 implements any of a range of management functions for maintainingfresh content. For example, cache 403 may invalidate portions of thecached content after an expiration period specified with the cached dataor by web sever 210. Also, cache 403 may proactively update the cachecontents even before a request is received for particularly important orfrequently used data from web server 210. Cache 403 evicts informationusing any desired algorithm such as least recently used, leastfrequently used, first in/first out, or random eviction. When therequested data is not within cache 403, a request is forwarded to webserver 210, and the returned data may be stored in cache 403.

Several types of packets will cause parser 404 to forward a requesttowards web server 201. For example, a request for data that is notwithin cache 403 (or if optional cache 403 is not implemented) willrequire a reference to web server 210. Some packets will comprise datathat must be supplied to web server 210 (e.g., customer creditinformation, form data and the like). In these instances, HTTP parser402 couples to data blender 404.

Optionally, front-end 201 implements security processes, compressionprocesses, encryption processes and the like to condition the receiveddata for improved transport performance and/or provide additionalfunctionality. These processes may be implemented within any of thefunctional components (e.g., data blender 404) or implemented asseparate functional components within front-end 201. Also, parser 402may implement a prioritization program to identify packets that shouldbe given higher priority service. A prioritization program requires onlythat parser 402 include a data structure associating particular clients205 or particular TCP packet types or contents with a prioritizationvalue. Based on the prioritization value, parser 402 may selectivelyimplement such features as caching, encryption, security, compressionand the like to improve performance and/or functionality. Theprioritization value is provided by the owners of web site 210, forexample, and may be dynamically altered, statically set, or updated fromtime to time to meet the needs of a particular application.

Blender 404 slices and/or coalesces the data portions of the receivedpackets into a more desirable “TMP units” that are sized for transportthrough the TMP mechanism 202. The data portion of TCP packets may rangein size depending on client 205 and any intervening links couplingclient 205 to TCP component 401. Moreover, where compression is appliedthe compressed data will vary in size depending on the compressibilityof the data. Data blender 404 receives information from front-endmanager 207 that enables selection of a preferable TMP packet size.Alternatively, a fixed TMP packet size can be set that yields desirableperformance across TMP mechanism 202. Data blender 404 also marks theTMP units so that they can be re-assembled at the receiving end.

Data blender 404 also serves as a buffer for storing packets from allclients 205 that are associated with front-end server 201. Blender 404mixes data packets coming into front-end server 201 into a cohesivestream of TMP packets sent to back-end server 203 over TMP link 202. Increating a TMP packet, blender 404 is able to pick and choose amongstthe available packets so as to prioritize some packets over others.

In an exemplary implementation, a “TMP connection” comprises a pluralityof “TCP connection buffers”, logically arranged in multiple “rings”.Each TCP socket maintained between the front-end server 201 and a client205 corresponds to a TCP connection buffer. When a TCP connection bufferis created it is assigned a priority. For purposes of the presentinvention, any algorithm or criteria may be used to assign a priority.Each priority ring is associated with a number of TCP connection bufferhaving similar priority. In a specific example, five priority levels aredefined corresponding to five priority rings. Each priority ring ischaracterized by the number of connection buffers it holds (nsockets),the number of connection buffers it holds that have data waiting to besent (nReady) and the total number of bytes of data in all theconnection buffers that it holds (nBytes).

When composing TMP data packets, the blender goes into a loop comprisingthe steps:

1) Determine the number of bytes available to be sent from each ring(nBytes), and the number of TCP connections that are ready to send(nReady)

2) Determine how many bytes should be sent from each ring. This is basedon a weight parameter for each priority. The weight can be thought of asthe number of bytes that should be sent at each priority this timethrough the loop.

3) The nsend value computed in the previous step reflects the weightedproportion that each ring will have in a blended TMP packet, but thevalues of nSend do not reflect how many bytes need to be selected toactually empty most or all of the data waiting to be sent a singleround. To do this, the nSend value is normalized to the ring having themost data waiting (e.g., nbytes=nSendNorm). This involves a calculationof a factor: S=nBytes/(Weight*nReady) for the ring with the greatestnReady. Then, for each ring, calculate nReady*S*Weight to get thenormalized value (nSendNorm) for each priority ring.

4) Send sub-packets from the different rings. This is done by taking asub-packet from the highest priority ring and adding it to a TMP packet,then adding a sub-packet from each of the top two queues, then the topthree, and so on.

5) Within each ring, sub-packets are added round robin. When asub-packet is added from a TCP connection buffer the ring is rotated sothe next sub-packet the ring adds will come from a different TCPconnection buffer. Each sub-packet can be up to 512 bytes in aparticular example. If the connection buffer has less than 512 byteswaiting, the data available is added to the TMP packet.

6) When a full TMP packet (roughly 1.5 kB in a particular example) isbuilt, it is sent. This can have three or more sub packets, depending ontheir size. The TMP packet will also be sent when there is no more dataready.

TMP mechanism 405 implements the TMP protocol in accordance with thepresent invention. TMP is a TCP-like protocol adapted to improveperformance for multiple channels operating over a single connection.Front-end TMP mechanism 405 and corresponding back-end TMP mechanism 505shown in FIG. 5 are computer processes that implement the end points ofTMP link 202. The TMP mechanism in accordance with the present inventioncreates and maintains a stable connection between two processes forhigh-speed, reliable, adaptable communication.

TMP is not merely a substitute for the standard TCP environment. TMP isdesigned to perform particularly well in environments such as theInternet. TMP connections are made less often than TCP connections. Oncea TMP connection is made, it remains up unless there is some kind ofdirect intervention by an administrator or there is some form ofconnection breaking network error. This reduces overhead associated withsetting up, maintaining and tearing down connections normally associatedwith TCP.

Another feature of TMP is its ability to channel numerous TCPconnections through a single TMP pipe 202. The environment in which TMPresides allows multiple TCP connections to occur at one end of thesystem. These TCP connections are then mapped into a single TMPconnection. The TMP connection is then broken down at the other end ofthe TMP pipe 202 in order to traffic the TCP connections to theirappropriate destinations. TMP includes mechanisms to ensure that eachTMP connection gets enough of the available bandwidth to accommodate themultiple TCP connections that it is carrying.

Another advantage of TMP as compared to traditional protocols is theamount of information about the quality of the connection that a TMPconnection conveys from one end to the other of a TMP pipe 202. As oftenhappens in a network environment, each end has a great deal ofinformation about the characteristics of the connection in onedirection, but not the other. By knowing about the connection as awhole, TMP can better take advantage of the available bandwidth.

In contrast with conventional TCP mechanisms, the behavior implementedby TMP mechanism 405 is constantly changing. Because TMP obtainsbandwidth to host a variable number of TCP connections and because TMPis responsive information about the variable status of the network, thebehavior of TMP is preferably continuously variable. One of the primaryfunctions of TMP is being able to act as a conduit for multiple TCPconnections. As such, a single TMP connection cannot behave in the samemanner as a single TCP connection. For example, imagine that a TMPconnection is carrying 100 TCP connections. At this time, it loses onepacket (from any one of the TCP connections) and quickly cuts its windowsize in half (as specified for TCP). This is a performance reduction on100 connections instead of just on the one that lost the packet.

Each TCP connection that is passed through the TMP connection must get afair share of the bandwidth, and should not be easily squeezed out. Toallow this to happen, every TMP becomes more aggressive in claimingbandwidth as it accelerates. Like TCP, the bandwidth available to aparticular TMP connection is measured by its window size (i.e., thenumber of outstanding TCP packets that have not yet been acknowledged).Bandwidth is increased by increasing the window size, and relinquishedby reducing the window size. Up to protocol specified limits, each timea packet is successfully delivered and acknowledged, the window size isincreased until the window size reaches a protocol specified maximum.When a packet is dropped (e.g., no acknowledge received or a resendpacket response is received), the bandwidth is decreased by backing offthe window size. TMP also ensures that it becomes more and moreresistant to backing off (as compared to TCP) with each new TCPconnection that it hosts. A TMP should not go down to a window size ofless than the number of TCP connections that it is hosting.

In a particular implementation, every time a TCP connection is added to(or removed from) what is being passed through the TMP connection, theTMP connection behavior is altered. It is this adaptation that ensuressuccessful connections using TMP. Through the use of the adaptivealgorithms discussed above, TMP is able to adapt the amount of bandwidththat it uses. When a new TCP connection is added to the TMP connection,the TMP connection becomes more aggressive. When a TCP connection isremoved from the TMP connection, the TMP connection becomes lessaggressive.

TMP pipe 202 provides improved performance in its environment ascompared to conventional TCP channels, but it is recognized that TMPpipe 202 resides on the open, shared Internet in the preferredimplementations. Hence, TMP must live together with many protocols andshare the pipe efficiently in order to allow the other transportmechanisms fair access to the shared communication bandwidth. Since TMPtakes only the amount of bandwidth that is appropriate for the number ofTCP connections that it is hosting (and since it monitors the connectionand controls the number of packets that it puts on the line), TMP willexist cooperatively with TCP traffic. Furthermore, since TMP does abetter job at connection monitoring than TCP and TMP is better suited tothroughput and bandwidth management than TCP.

Also shown in FIG. 4 are data filter component 406 and HTTP reassemblecomponent 407 that process incoming (with respect to client 205) data.TMP mechanism 405 receives TMP packets from TMP pipe 202 and extractsthe TMP data units. Using the appended sequencing information, theextracted data units are reassembled into HTTP data packet informationby HTTP reassembler 407. Data filter component 406 may also implementdata decompression where appropriate, decryption, and handle cachingwhen the returning data is of a cacheable type.

FIG. 5 illustrates principle functional components of an exemplaryback-end 203 in greater detail. Primary functions of the back-end 203include translating transmission control protocol (TCP) packets from webserver 210 into TMP packets as well as translating TMP packets receivedfrom a front-end 201 into the one or more corresponding TCP packets tobe send to server 210.

TMP unit 505 receives TMP packets from TMP pipe 202 and passes them toHTTP reassemble unit 507 where they are reassembled into thecorresponding TCP packets. Data filter 506 may implement otherfunctionality such as decompression, decryption, and the like to meetthe needs of a particular application. The reassembled data is forwardedto TCP component 501 for communication with web server 210.

TCP data generated by the web server process are transmitted to TCPcomponent 501 and forwarded to HTTP parse mechanism 502. Parser 502operates in a manner analogous to parser 402 shown in FIG. 4 to extractthe data portion from the received TCP packets, perform optionalcompression, encryption and the like, and forward those packets to datablender 504. Data blender 504 operates in a manner akin to data blender404 shown in FIG. 3 to buffer and prioritize packets in a manner that isefficient for TMP transfer. Priority information is received by, forexample, back-end manager 209 based upon criteria established by the website owner. TMP data is streamed into TMP unit 505 for communication onTMP pipe 202.

FIG. 7 illustrates a conceptual diagram showing entity relationshipsmaintained by the system in accordance with the present invention. InFIG. 7, client 205 is an HTTP client of the web server or serversimplementing web site 210. Virtual network 200 is defined by the networkof front-end servers 201 and back-end servers 203 in accordance with thepresent invention that are illustrated by stars along the periphery ofvirtual network 200. There may be many hundreds or thousands of thesefront-end servers 201 and back-end servers 203 making the reach ofvirtual network 200 substantially coextensive with Internet 101 itself.

The present invention involves two conceptual redirection activities.First, a client request for the web site at domain “abc.com” must beredirected to virtual network 200. This first level of redirection doesnot select a particular front-end server 201, but instead involves theredirection to the virtual network 200 which comprises the collection ofarbitrary front-end servers 201. For purposes of discussion, virtualnetwork 200 is within a domain “redir.abc.com” although it should beunderstood that virtual network 200 is shared across every domain thathas a web site 210 coupled to a back-end server 203. A secondredirection activity involves selecting a particular channel 202 suchthat all subsequent communication between client 205 and web site 210 isconducted over the selected channel.

One or more back-end servers 203 have a persistent relationship orassignment to web site 210. In contrast, any of the available front-endservers 201 may be dynamically connected to the back-end 203 assigned toa particular site. The first level of redirection can be accomplished ina number of ways. As described hereinbefore, the public DNS administeredby InterNIC can be informed that the domain “abc.com” is to beadministered by redirector 601 rather than a conventional DNS. Thisrequires a web site owner to turn over control of all or a portion ofits domain name to the administrator of redirector 601. It iscontemplated that only a portion may be turned over by the owner ofabc.com. (e.g., abc.def.com is turned over, but ghi.def.com isretained). The first level of redirection is then handled by the upperlevel public DNS system as shown in FIG. 6 where InterNic 610 referencesredirector 601 during the resolution process.

Alternatively, web site 210 can retain control over the domain name“abc.com” and explicitly redirect as desired by responding to theinitial (or any subsequent) HTTP request with a reference to“redir.abc.com”. The domain “redir.abc.com” refers only to a virtualnetwork 200 and not to a physical machine. However, “redir.abc.com” isregistered with Internic 610 to be resolved by redirector 601. In thismanner, the administrator of web site 210 can determine at what point aclient 205 is redirected into the enhanced communication channels 202made available by virtual network 200.

Although the invention has been described and illustrated with a certaindegree of particularity, it is understood that the present disclosurehas been made only by way of example, and that numerous changes in thecombination and arrangement of parts can be resorted to by those skilledin the art without departing from the spirit and scope of the invention,as hereinafter claimed. For example, while devices supporting HTTP datatraffic are used in the examples, the HTTP devices may be replaced oraugmented to support other public and proprietary protocols includingFTP, NNTP, SMTP, SQL and the like. In such implementations the front-endserver 201 and/or back end 203 are modified to implement the desiredprotocol. Moreover, front-end server 201 and back-end server 203 maysupport different protocols such that the front-end server 201 supports,for example, HTTP traffic with a client and the back-end server supportsa DBMS protocol such as SQL. Such implementations not only provide theadvantages of the present invention, but also enable a client to accessa rich set of network resources with minimal client software.

1. A system for serving web pages to a requesting software application comprising: a web site; a plurality of front-end servers, wherein a unique network address is assigned to each front-end server; a first channel configured to support request and response communication between the software application and the web site; a plurality of second channels configured to support communication between each of the front-end servers and the web site; a redirector server operable to select one front-end server from the plurality of front-end servers and generate a response referring the requesting software application to the selected front-end server, wherein the redirector server determines a composite quality factor based on at least partially two or more component factors for the plurality of second channels and selects the selected one front-end server at least partially based upon the relative composite quality factors of the plurality of second channels; and mechanisms within the web site for redirecting a request received from the software application on the first channel to the redirector server.
 2. The system of claim 1 wherein the web site is located in a first address domain and the plurality of front-end servers are located within a second address domain.
 3. The system of claim 1 further comprising: mechanisms within at least some of the front-end servers for implementing a portion of the web site, wherein the redirector server selects amongst the plurality of front-end servers based upon a relative ability of the front-end servers to implement the web site without reference to the first address domain.
 4. The system of claim 1 wherein the first communication channel comprises an Internet standard communication channel and the second channel comprises an enhanced communication channel linking at least one of the plurality of front-end servers with the web site.
 5. The system of claim 1 wherein the redirector server further determines a communication quality factor for the communication channel for at least one front-end and the requesting software application and selects the selected one front-end at least partially based upon the relative communication quality factors of the channels between the plurality of front end servers and the requesting software application.
 6. The system of claim 1 wherein the redirector server comprises a multi-tiered set of redirector servers including: a global redirector which is registered with a public domain name system as a domain name server for the domain name of the web site; a plurality of regional redirectors, wherein each regional redirector is registered with the global redirector as a domain name server for a particular topographical region; and a plurality of network redirectors, wherein each network redirector is associated with a subset of front-ends and is registered with each of the regional redirectors as a domain name server for the associated subset of front-ends.
 7. The system of claim 6 wherein the global redirector selects amongst the regional redirectors based upon an estimated user location indicated by the network address supplied by the requesting software application.
 8. The system of claim 6 wherein the regional redirectors select amongst the plurality of network redirectors based upon an estimated user location indicated by the network address supplied by the requesting software application.
 9. The system of claim 6 wherein the network redirectors select amongst the plurality of front-ends at least partially based upon a calculated index comparing the estimated quality of service that can be provided by each of the front-ends in the subset of front-ends associated with the network redirector.
 10. The system of claim 6 wherein the network redirectors select amongst the plurality of front-ends at least partially based upon a comparison of content and/or services provided by the front-ends.
 11. The system of claim 1 wherein the redirector server generates a response referring the requesting software application to a secure port of the selected front-end server.
 12. A method for redirecting a communication between a software application and a network resource over a communication network, the method comprising: causing a software application to generate a first DNS (“domain name system”) request over a first channel within the communication network, the first request specifying a domain name of the network resource; selecting a second channel within the communication network that supports communication with the network resource; responding to the DNS request with a network address of a front-end machine that supports the selected second channel; conducting subsequent communications between the software application and the network resource over the second channel; and causing the network resource to generate a redirect message in response to the first request, the redirect response identifying a redirector server to perform the responding to the DNS request.
 13. The method of claim 12 further comprising: causing the software application to generate a second request directed to the redirector server; and causing the redirector server to generate a message in response to the second request, the message identifying a selected one of a plurality of front-end servers that are configured to implement the second channel.
 14. The method of claim 12 wherein the first request is resolved by a public domain name system to identify a network address of a global redirector server that is registered with the public domain name service as a domain name server for the domain name of the network resource.
 15. The method of claim 12 wherein the plurality of front-end servers are located within a first address domain different from an address domain in which the network resource is located.
 16. The method of claim 12 wherein the act of responding to the DNS request with a network address of a front-end machine that supports the second channel further comprises responding with a secure port address of the front-end machine. 